Novel fire-retardant polymer

ABSTRACT

A new cellular thermosetting synthetic polymer prepared by heating the polymerized foamed product derived from the reaction of an aminophenyl ethanol and an unsaturated dicarboxylic anhydride. 
     The new synthetic polymer has self-extinguishing properties and exhibits low smoking characteristics and is useful as flame retardant insulation.

BACKGROUND OF THE INVENTION

This invention relates to a new chemical compound, namely,poly[N-(3-vinylphenyl)maleimide], to a process for the preparation ofsaid compound, and to the use of said compound in the fire-retardantarea.

In the preparation of most self-extinguishing materials, it is oftennecessary to chemically bind a halogenated compound and crosslinkablecompound. Unfortunately, upon combustion these materials still generatesubstantial amounts of smoke containing varying amounts of toxic gases.

It has now been found that a synthetic polymer can be produced which isinherently low smoking, nondripping, and self-extinguishing. Due to itsunique self-extinguishing characteristics, this polymeric compound canbe utilized in numerous areas wherein self-extinguishing material isrequired.

The test employed herein to demonstrate self-extinguishing properties ofthe polymer accurately is ASTM Test No. D-1692 and serves to exemplifythe self-extinguishing characteristic of the polymer when exposed tosmall scale ignition sources. It is well recognized by those skilled inthe art, and should be clearly understood by others, that all organicpolymers will burn when subjected to a sufficiently intense heat source(whether or not they contain fire-retardant additives or properties).

SUMMARY OF THE INVENTION

Poly[N-(3-vinylphenyl)maleimide] can be prepared by the dehydration ofthe hydroxyethyl functionality ofpoly[N-(3-(1-hydroxyethyl)phenyl)maleimide], saidpoly[N-(3-(1-hydroxyethyl)phenyl)maleimide] being prepared by thepolymerization of m-1-(hydroxyethyl) maleanilic acid, with theconcurrent dehydration of the amic acid functionality to a cyclic imide.

DETAILED DESCRIPTION

According to a preferred embodiment the m-1-(hydroxyethyl) maleanilicacid can be prepared from an aminophenyl ethanol and an unsaturateddicarboxylic anhydride. Such preparation is accomplished by firstdissolving a stoichiometric amount of maleic anhydride in a suitablesolvent, e.g. chloroform. An equivalent amount of hydroxyethyl anilineis also dissolved in a separate amount of suitable solvent, e.g.chloroform. The hydroxyethyl aniline solution is then added to areaction vessel equipped with a stirrer, a condenser, and an additionfunnel. The maleic anhydride solution is added at such a rate that theresulting exothermic reaction is controlled. The resultant product,m-1-(hydroxyethyl)maleanilic acid is suction filtered, washed withchloroform, benzene, or other suitable solvents, and dried. The driedproduct is a yellow solid with a melting point of 169°-171° C. Themaleanilic acid is then polymerized formingpoly[N-(3-(1-hydroxyethyl)phenyl)maleimide]. This thermoplastic polymeris formed because of the dehydration which occurs concurrent with thepolymerization process. Due to the release of water during thepolymerization of the maleanilic acid,poly[N-(3-(1-hydroxyethyl)phenyl)maleimide] is obtained as a foam whensuch polymerization is carried out at atmospheric pressure. Suchdehydration transforms the amic acid functionality of the maleanilicacid to a cyclic imide. Further dehydration of the hydroxyethylfunctionality gives rise to the instant crosslinked polymer,poly[N-(3-vinylphenyl)maleimide]. The reaction may be illustrated asfollows: ##STR1##

Exemplary of monomers which may be substituted for maleic anhydride arecitraconic anhydride and the halogenated derivatives of both citraconicand maleic anhydride.

Illustrative of substitutes for m(alpha-hydroxyethyl)aniline, areisomeric hydroxyethyl anilines and their substituted derivatives. Saidsubstitutes are illustrated as follows: ##STR2## wherein m is an integerfrom 1 to 5, n is an integer from 0 to 4, and wherein X is a halogen, analkyl or an aromatic group.

The following example illustrates the invention.

EXAMPLE 1

A sample of the maleanilic acid is placed in an oven for 60 minutes at175° C. The resulting maleimide is a soluble cellular polymer which isyellow or orange in color. (Said polymer is formed through the C=Cdouble bond. The hydroxyl on the ethyl group remains unchanged as shownby infrared spectroscopy). A portion of this material is then placed inan oven for 30 minutes at 280° C producingpoly[N-(3-vinylphenyl)maleimide], a brown, insoluble cellular polymerwhich had been dehydrated through the ethyl group leading to thecrosslinked polymer. This crosslinked polymer is placed in a flame. Itis found to be nondripping, low smoking and self-extinguishing (ASTMTest No. 1692) and can be useful as a flame retardant insulation.

What is claimed is:
 1. Cross-linked poly[N-(3-vinylphenyl)maleimide]. 2.A process for the preparation of poly[N-(3-vinylphenyl)maleimide]comprising polymerizing the product derived from the reaction of anaminophenyl ethanol and an unsaturated dicarboxylic anhydride, thensubjecting the polymerized product to a heat source sufficient to causecross-linking.
 3. Process of claim 2 wherein the aminophenyl ethanol isselected from the group consisting of hydroxyethyl aniline, isomerichydroxyethyl anilines, and the halogenated, alkylated, and aromaticsubstituted derivatives of both hydroxyethyl aniline and isomerichydroxyethyl aniline.
 4. Process of claim 3 wherein the unsaturateddicarboxylic anhydride is selected from the group consisting of maleicanhydride, citraconic anhydride, and the halogenated derivatives ofcitraconic and maleic anhydride.
 5. Process of claim 4 wherein thereaction product of an aminophenyl ethanol and an unsaturateddicarboxylic anhydride is m-1-(hydroxyethyl) maleanilic acid.
 6. Processof claim 2 wherein the polymer derived from the polymerization ofm-1-(hydroxyethyl) maleanilic acid ispoly[N-(3-(1-hydroxyethyl)phenyl)-maleimide].